'I used to be scared to go out because I knew if I met friends for dinner, I would spend half the night feeling ill and looking for the nearest toilet," says Dublin office worker Katarzyna Morawska.

"Even getting ready to go out was a problem. My stomach was often so bloated I looked like I was eight months pregnant and couldn't fit in my clothes. I felt like I had stones inside me, or as if someone was poking and squeezing my stomach.

"I couldn't go out and enjoy myself but I didn't know why."

It was a situation that had been getting progressively worse for several years. Katarzyna, a 31-year-old Polish project manager who has been living in Dublin for the past seven years, frequently suffered from agonising stomach cramps, bloating, diarrhoea, hot flushes and dizzy spells.

After visiting her GP, she was referred to St Vincent's Hospital where both a gastroscopy and colonoscopy (internally examining the stomach, intestines and colon) revealed no problems.

Perplexed and anxious that nothing explained her very real symptoms, it was only as she got ready to leave the hospital that a nurse suggested getting a food intolerance test.

Food intolerances have become increasingly trendy in recent years thanks to the proliferation of celebrities on dairy and wheat free diets. But they're not a new phenomenon.

Since the early 1920s, research has probed the possibility that multiple illness complaints, not verifiable by scientific diagnosis, could be caused by prolonged exposure to eating foods the body lacks the correct enzymes to digest.

Today, it's estimated that around one in five people in Ireland suffer from a food intolerance, with the most common food triggers being dairy products, wheat, barley, gluten, beef, eggs, citrus fruits, nuts and shellfish.

But, perhaps because it's not always seen as part of conventional medicine, many more people could be suffering and not realise it.

He adds: "We carry out around 100 tests a week but it's very sad to think that so many more people could be helped if they only knew about food intolerance testing.

"My filing cabinets are filled with people whose lives have been dramatically helped, and the potential cost savings for the health service, by identifying this cause, is potentially very large."

According to Healy, many conditions at present treated with repeat courses of antibiotics respond very well to food elimination diets.

In fact, antibiotics could actually be having a negative effect on the root cause of the problem by disturbing the balance of gut bacteria.

How the food test works is by testing a small blood sample to measure the amount of food specific IgG antibody in it.

For €135, blood can be tested against 40 foods, or against 93 for €255. The higher the antibody levels, the more sensitive the person is to that food.

The Fitzwilliam also offers home testing kits, and many Boots outlets also run a food intolerance testing service.

Just 10 days after taking the food intolerance test, Katarzyna's results came back revealing she was intolerant to dairy.

"I cut out milk, yogurt and eggs and straight away noticed a difference," she enthuses.

"I had no bloating, my tummy was flat, I wasn't running to the toilet, and I could wear my clothes again!"

With so many shops offering 'free-from' ranges, she's found it easy to swap to a dairy-free lifestyle, and friends always make sure they have almond milk in the fridge if she calls round for a cup of coffee.

"I feel so much better," she beams, "I'm not scared to go out any more. It had got to the point where I didn't even want to leave my office at lunchtime because I was worried about being too far from the toilets.

"I've only had to make little changes to what I eat, but it's made a big difference to how I live – it's changed my life."